Currently, conventional printing or large-volume copying of reliefs with functional surfaces, e.g. optical reliefs with diffractive surface, refractive surface, with refraction or data, use templates (masters) that modify the incident light wave. The masters are nearly exclusively made of metal, nickel, chromium, steel, copper etc. and if the printing resolution is relatively low (with the smallest detail size 10 to 20 μm) then they can be made of plastic. Masters for copying of optical structures with very fine reliefs are made by galvanization as a foil (metal sheet). The metal sheet is grown on a cathode that is used as a template for the master. The method is disadvantageous due to the size limitations of galvanic baths. In case of rotation copying a metal sheet or foil is stretched on a cylinder but this results in visible joints (links) when individual parts are connected. When printing colors on paper or plastic the motif is developed on cylinders (photogravure) or using a technique similar to multiplication of optical structures, e.g. flexoprint for low resolutions or intaglio (printing block—metal sheet made by galvanoplasty, stretched on cylinders) or offset printing. One disadvantage is that it is very difficult to achieve a higher resolution, below the size of the smallest detail 10 μm.
Paper, plastic and printing inks are complemented with security elements. The elements are supposed to aggravate potential forgery and they are also used for fast or official verification of authenticity. They are mainly special pigments that change color depending on the observation angle (optically variable inks), fibers or particles with color effects in visible or ultraviolet light, pigments, fibers or particles that change infrared light to visible light (the so-called anti-stokes pigments), microparticles that can be oriented in magnetic field, active in infrared light etc. A recent method that is still under development involves use of identification microparticles that bear specific information on the surface connected with the user (e.g. logo), production time, application etc.
The information on the surface of such objects is applied by sophisticated technologies, mostly in form of graphic diffractive or non-diffractive recordings (e.g. JDSU, Optaglio). The demanding manufacturing process also influences the price. Another limitation consists in the fact that security microparticles with information on the surface, due to the materials used up to now, i.e. particularly metals and plastics, are difficult to combine with other materials with other effects that can be achieved by addition of the above-mentioned optically active substances which are common on the markets and to which the users are accustomed to.